1. Field of the Invention
The present invention relates to a spread illuminating apparatus, and more particularly to a spread illuminating apparatus used as an illuminating means for a liquid crystal display device.
2. Description of the Related Art
A demand for a liquid crystal display device operating in a low power consumption is increasing mainly for a computer-related field due to its low profile and light weight. However, since a liquid crystal of the liquid crystal display device does not emit light by itself unlike a light emitting element such as a cathode-ray tube, a separate illuminating means is required for an image observation. In particular, a spread illuminating apparatus of side light type (light conductive plate type) is used as an illuminating means for the liquid crystal display device for satisfying a recent demand of the low profile.
FIGS. 5 to 7 show an example of a side light type spread illuminating apparatus.
As shown in FIGS. 5 and 6, a spread illuminating apparatus 1 generally comprises a transparent substrate (a guide plate) 2 made of a light-transmissible material, a bar-like light source 3 disposed close to an end surface 2a of the transparent substrate 2, and a frame 4 on which the transparent substrate 2 and the light source 3 are mounted.
The light source 3 generally comprises a bar-like light conductive member (a guide rod) 5 made of a transparent material and disposed along and close to the end surface 2a of the transparent substrate 2, an LED 6 (a spot-like light source) disposed facing one end 5a of the light conductive member 5 and mounted on a flexible printed circuit board (hereinafter referred to as FPC) 8 together with the light conductive member 5, and a reflection plate 7 (to be discussed hereinbelow) disposed facing another end 5b of the light conductive member 5 and mounted on the FPC 8 together with the light conductive member.
The FPC 8 has a substantially elongate rectangular FPC main body 8a on which the light conductive member 5, the LED 6 and the reflection plate 7 are mounted. An extension having a connecter on a tip thereof is provided at the FPC main body 8a, though not shown in the figure.
The frame 4 comprises a substrate mounting section 10 shaped rectangular and adapted to mount the transparent substrate 2 on, and an FPC mounting section 11 shaped elongatedly rectangular, disposed in contact with the substrate mounting section 10 and adapted to receive the FPC main body 8a. The longitudinal dimension of the FPC mounting section 11 is set to be larger than the width of substrate mounting section 10.
A wall 12 is provided vertically at one end (the lower side in FIG. 6) of the substrate mounting section 10 as shown in FIG. 6. Further, a wall 13 is provided vertically at one end (an upper side in FIGS. 6 and 7) of the FPC mounting section 11 as shown in FIGS. 6 and 7.
Though not shown in the figures, the extension having a connector on the tip thereof is provided at a side of the FPC main body facing transparent substrate, and an opening through which the extension passes is formed at a flat area where the substrate mounting section and the FPC mounting section of the frame meet with each other.
In the above conventional art, the upper surface of the light conductive member 5 and the upper surface of the transparent substrate 2 are not flush with each other due to the thickness of the FPC 8. Thus, the coupling efficiency of light emitted from the light conductive member 5 and guided in the transparent substrate 2 (hereinafter referred to as xe2x80x9clight coupling efficiencyxe2x80x9d) is degraded.
The present invention has been made in the light of the above problem. Accordingly, it is an object of the present invention to provide a spread illuminating apparatus which can improve the light coupling efficiency between the light conductive member and the transparent substrate.
In order to solve the above problem, according to a first aspect of the present invention, in a spread illuminating apparatus comprising a transparent substrate which is made of a light-transmissible material, a bar-like light source which comprises a bar-like light source made of a transparent material and a spot-like light source disposed on at least one end of the light conductive member and mounted on an FPC together with the light conductive member and is disposed along and close to at least one end surface of the transparent substrate, and a frame on which the light conductive member and the spot-like light source both mounted on the FPC are mounted together with the transparent substrate, the frame is structured such that an FPC mounting section, on which an FPC main body shaped elongatedly rectangular and having the light conductive member and the spot-like light source arranged thereon is mounted, is lower by a predetermined dimension than a substrate mounting section, on which the transparent substrate is mounted.
In order to solve the above problem, according to a second aspect of the present invention, in the spread illuminating apparatus according to the first aspect of the present invention, the predetermined dimension is equal to a thickness of the FPC.
In order to solve the above problem, according to a third aspect of the present invention, in the spread illuminating apparatus according to the first or the second aspect of the present invention, an extension which has a connector on its tip is provided at a side of the FPC main body facing the transparent substrate, and an opening through which the extension passes is formed at a stepped part which constitutes a boundary between the substrate mounting section and the FPC mounting section in the frame.